A 55-metre Long Image of Our Milky Way Galaxy

Imagine an image 55 metres long… an image about half a football field long…

This is the 55-m mosaic of our galactic plane, broken up into five components, taken by NASA’s Spitzer Space Telescope in infrared. More than 800,000 snapshots have been stitched together to produce this family portrait of stars in our inner galaxy. The image depicts an area of sky 120 degrees wide by 2 degrees tall.

The top strip is the far-left side of the galactic plane; second to top is the area just left of the galactic centre; the middle strip is the galactic centre; second to bottom represents the area to the right of galactic centre; and the bottom one is the far-right side of the plane. These panels represent more than 50 percent of our entire Milky Way Galaxy.

The swaths of green represent organic molecules, while the heat from warm dust is rendered in red. Star-forming regions appear as swirls of red and yellow, where the warm dust overlaps with the glowing organic molecules. The blue specks sprinkled throughout the photograph are Milky Way stars. The bluish-white haze that hovers heavily in the middle panel is starlight from the older stellar population towards the centre of the galaxy.

When we look up at the night sky, we can see a band of light stretches across the night sky. That band, commonly known as the Milky Way Band, is actually the flat, dusty disk of our galactic plane. Our Earth resides in this disk, roughly 26,000 light years from the centre.

Since the disk is very dusty, we cannot see through the disk with visible light. However, we can use infrared telescopes to see what would otherwise be invisible because infrared light can penetrate the dust. So, with Spitzer’s dust-piercing infrared eyes, astronomers manage to look 60,000 light-years away into this fuzzy band, and saw all the way to the other side of the galaxy.

This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way. It catalogued more than 100 million stars. This data can help us understand how massive stars form, map the galactic spiral arms and make a better estimate of our galaxy’s star-formation fate.